Certain integrated circuits (xe2x80x9cICsxe2x80x9d) are designed to receive varying types of input signals. These input signals typically have varying types and levels of signal degradation. Signal degradation affects the speed with which a receiver is able to reliably respond. Speed of response, however, is an important feature in a receiver. It is possible to tune a receiver for fastest response if the type of signal degradation is known. Sufficient knowledge of the signal degradation characteristics, however, is typically not available or varies in the application for which the receiver is intended to function. Additionally, it is advantageous for an IC to be able to interoperate with other ICs in a wide variety of signal environments. As electrical circuits become faster and more sophisticated, the response time becomes more of a disadvantage and affects overall performance of the IC. Similarly, it is disadvantageous to require a level of signal quality within a narrow range of input signal characteristics. A requirement such as this forces compromises upstream of the receiver that may affect overall performance of a product into which the IC is used or may convince a buyer of the IC that an alternative product and vendor is preferable.
There is a need, therefore, for a receiver apparatus that is capable of accepting a wide variety of signal types and signal degradation while also capable of quick response.
In view of the need in the art, a receiver apparatus accepts an input signal and comprises first and second receivers, each receiver accepting the input signal and each receiver tuned for optimal response to a set of known input signal properties. Each receiver produces first and second intermediate signals respectively, one of the receivers produces a first transition. The apparatus further comprises first and second primary transition propagation elements, and a secondary transition propagation element. A preset signal prepares the first and second primary transition propagation elements and the secondary transition propagation element to propagate the first transition to an input of an output transition propagation element. The output transition propagation element accepts and propagates the first transition to an output of said output transition propagation element. A pass gate accepts a signal at an input of the pass gate, the signal being based upon the output of the output transition propagation element. The pass gate inhibits presentation of the signal at an output of the pass gate as the preset signal until the first and second intermediate signals are equivalent.
A method of propagating an input signal comprises the steps of accepting the input signal into a plurality of receivers to create a plurality of intermediate signals, one of which propagates a first transition. The method further comprises preparing first and second primary propagation elements and a secondary transition propagation element to propagate a first transition and propagating the first transition to an output. The method further comprises transmitting a signal based upon the output as a preset signal when all of the plurality of intermediate signals are equivalent and inhibiting the preset signal when the plurality of intermediate signals is not equivalent, and storing a previous preset signal until all of the plurality of intermediate signal is equivalent.
Advantageously, an apparatus and method according to the teachings of the present invention permits quick response to a transition at an input port and subsequent propagation of the transition to the output port while being able to process a wide variety of input signal properties.